1. Field
One embodiment of the present invention relates to a method of manufacturing a magnetic recording medium such as a discrete track recording medium and a bit patterned medium and a magnetic recording medium manufactured using the method.
2. Description of the Related Art
Recently, in the magnetic recording medium installed in hard disk drives (HDDs), there is an increasing problem of disturbance of enhancement of track density due to interference between adjacent tracks. In particular, a serious technical subject is reduction of write blurring due to fringe effect of a magnetic field from a write head.
To solve such a problem, a discrete track recording patterned medium (DTR medium) has been proposed in which recording tracks are physically separated from each other. Since the DTR medium can reduce a side-erase phenomenon in writing and a side-read phenomenon in reading, it can increase the track density. Therefore, the DTR medium is promising as a high-density magnetic recording medium.
Also, a bit patterned medium (BPM) has been proposed in which read and write are performed for a single magnetic dot as a single recording cell have been proposed.
When read and write of a medium having a surface on which patterns of protrusions and recessed are formed such as the DTR medium and BPM are performed with a flying head, it is preferable that the medium has a flattened surface. Here, it is desirable to make the magnetic recording layer as thick as at least 15 nm in order to ensure signal outputs. In this case, in order to completely separate adjacent tracks with each other, the magnetic recording layer should be etched over the thickness of 15 nm. On the other hand, a designed flying height of the flying head is approximately 10 nm. In order to ensure a head flying height in this state, it is necessary to reduce the width of recesses on the medium surface or to flatten the medium surface by filling the recesses with a nonmagnetic material. It is very difficult, however, to reduce the width of recesses from limitation of electron beam recorder. If the beam size of the EBR is 20 nm, for example, it is impossible to draw patterns having a size of 20 nm or less. To fill the recesses with a nonmagnetic material brings about high manufacturing cost.
On the other hand, there are studied methods of magnetically deactivating the magnetic recording layer in the areas corresponding to the separating regions between the magnetic patterns. For example, Japanese Patent No. 3886802 discloses a method of forming the separating regions between the magnetic patterns by making the magnetic recording layer reacted with halogen. Jpn. Pat. Appln. KOKAI Publication No. 5-205257 discloses a method of forming the separating regions between the magnetic patterns by implanting nitrogen or oxygen. Jpn. PCT National Publication No. 2002-501300 discloses a method of forming the separating regions between the magnetic patterns by applying He ions to the regions.
Since these methods magnetically deactivate the magnetic recording layer having a flat surface and a large thickness, they need a long period of time to form nonmagnetic separating regions. In the method of Jpn. Pat. Appln. KOKAI Publication No. 5-205257, if modification of the separating regions is insufficient, the separating regions have a relatively high coercivity which makes it impossible to separate the magnetic patterns effectively. In the method of Jpn. PCT National Publication No. 2002-501300, if modification of the separating regions is insufficient, it may cause magnetization reversal in the separating regions which also makes it impossible to separate the magnetic patterns effectively.
Jpn. Pat. Appln. KOKAI Publication No. 2005-42143 discloses a method of manufacturing a magnetic random access memory (MRAM) in which reactive ion etching (RIE) using alcohol is performed to etch the magnetic thin film. However, this method does not modify the magnetic thin film. Thus, when the method is applied to manufacturing of a patterned medium, it is needed to etch the magnetic recording layer over the entire thickness.